The land cover at various geographic locations is important for government and commercial uses and a vast array of satellite image products are now available for analysis. An area of increasing interest and concern is how to use satellite imagery for the assessment of local and global environmental changes. The extension of satellite remote sensing technology into these areas benefits society by providing a better understanding of the causes and consequences of pollution, global environmental change, land use change, natural disasters, etc. Thus, satellite imagery has increasingly been used as a data source to identify changes in geographic and environmental features.
Various systems have been developed to detect land cover changes. For example, U.S. Pat. No. 5,719,949 provides an information processing system that uses satellite image data in order to accurately identify changes in the studied areas. The system relies upon a vectorized database which has been classified according to land cover features. Change is defined by a Z-statistic. The Z-statistic is calculated in a two-pass cross-correlation technique when pixel brightnesses are compared to a mean brightness for the typical land cover class and to a standard deviation for that class. The normalized difference values are accumulated across different bands, are scaled and then compared to a threshold which defines high, medium and low change values. A map is produced illustrating areas of significant change.
Changes in land cover may be considered transient or persistent. For example, man-made or anthropomorphic features such as the new building and road construction or other soil disturbance tend to be persistent changes. However, many changes that are identified turn out to be transient or seasonal in nature. For example, crops may be rotated, leaves may be on or off of deciduous trees and snow, rain or other weather conditions may appear as changes in land cover. Thus, the identification of changes in land cover by various change detection systems may not distinguish between transient or cyclical changes in comparison to what may be persistent changes.